Control mechanism for electrically operated liquid fuel burners



g- 1933- w. w. WILLIAMS 1,923,651

CONTROL MECHANISM FOR ELECTRICALLY OPERATED LIQUID FUEL BURNERSOriginalfiled Oct. 5, 1928 2 Sheets-Sheet 1 IN VEN TOR. WHL 75/? W. W/LLlfl/WS TTORNEYS.

Patented Aug. 22, 1933 CONTROL MECHANISM FOR ELECTRICALLY OPERATEDLIQUIDFUEL BURNERS Walter W. Williams, Bloomington, Ill., assignor toWilliams Oil-O-Matic Heating Corporation,

Bloomington, 111., a Corporation of Illinois Original applicationOctober 3, 1928, Serial No.

310,159. Divided and this application January 16, 1932. Serial No.587,060

1 Claim. (01. 158-28) This invention relates to improvements in controlmechanism for electrically-operated liquid fuel burners and moreparticularly to a control mechanism for domestic electrically-operated 5fuel burners such as illustrated and described in my prior pendingapplication Serial No. 286,314, filed June 18, 1928 which matured Nov.8, 1932 into Letters Patent No. 1,886,998. This application is adivision of the applic'ants prior copending application, Serial No.310,159, filed October 3, 1928 which maturedv February 16, 1932, intoLetters Patent 1,845,823.

It is an object of this invention to provide a pressure actuated circuitcloser so constructed that an increase in pressure will throw thecircuit closer mechanism to one position and thereafter allow a furtherincrease .in pressure to act freely beyond'the degree necessary toactuate the mechanism, without injury to the mechanism, and

upon a decrease in pressure from whatever degree to immediately actuatethe mechanism to throw the closer to the opposite position.

It is a further object of this invention to providea control in a deviceof the character specified which will so operate, when the controlcircuit is closed, to start the motor in operation to furnish air beforethe fuel valve is opened to furnish fuel.

While the preferred forms of this invention are illustrated upon theaccompanying drawings, it is to be understood that minor detail changesmay be made without departing from the scope thereof.

In the drawings: H

Figure 1 is a view in side elevation illustrating an embodiment ofthis-invention as applied to an electrically operated domestic liquidfuel burning device.

Figure 2 is an enlarged detail end elevation, 40 with the coversremoved, illustrating the transformer and electrical connection to themotor and the improved control mechanism.

Figure 3 is a Wiring diagram of this improved control as applied to'thetype of domestic liquid v fuel burner illustrated in Figure 1.

Figure 4 is an enlarged detail view in end elevation of the improvedcontrol mechanism.

Figure 5 is a top plan view of Figure 4.

Figure 6 is a vertical sectional view taken upon the line 5-5 of Figure5 looking in the direction of the arrows.

The embodiment of this improved control illustrated in Figure 1 itsapplication to a domestic electrically-operated liquid fuel burningdevice of the type illustrated and described in my above said co-pendingapplication and therefore the construction and operation of the fuelburner need be but briefly described. A motor contained within thecasing 1 operates a fan blower therebelow in a casing for providingadditional air through the conduit 2 leading from said blower casing tothe fuel combustion chamber within the cylindrical casing 3. The casing4 contains a liquid fuel control apparatus including a valve having astem 5 projecting thereabove, which controls the admission of the fuelfrom the source to the fuel combustion chamber within the casing 3.

I A transformer 6 is mounted in a casing 6 carried upon the exteriorside of the motor casing; as shown at the right hand of.Fig1 1re 1. Theim.- proved control mechanism is preferably mounted in a cylindricalcasing 7 upon the upper side of the transformer casing and ispreferablyprovided with a cover 8, as shown in Figure 1,

Referring to the enlarged detail views illustrated in Figures 4, 5, and6, and particularly the sectional view shown in Figure 6, thecylindrical casing 7 is closed by a circular plate 9. An electricalheating unit 10, preferably comprising a section of resistance wirewrapped about 'a flat plate, is arranged upon the bottom of this casing,and resting upon the heating unit is an expansible and contractibleelement 11, preferably of cylindrical form and containing a liquid orgas which readily expands or contracts upon changes in temperature. Itis preferable to maintain the lower side of the expansible andcontractible member 11 in fixed relation by supporting it upon acentrally located post 12 mounted upon the bottom 13 of the cylindricalcasing 7. A centrally located operating shaft 14 is arranged to bearupon the expansible and contractible member on the side opposite thefixed post' 12 and to pass through a central opening provided thereforin the cover plate 9. The operating shaft 14 is caused to move up anddown as the expansible member expands and contracts by soldering orotherwise securing the end of the shaft to the member 11, or the shaftmay be maintained in contact with the member 11 by securing a'fiat disc11 on the end thereof and interposing a coil spring ll 'between' theupper sideof the disc and lower side of the cover 9, as shown.

A switch operating mechanism is mounted upon a. bracket 15 extendingupward about the center of, and secured upon, the cover plate 9. Thebracket 15 supports a horizontal shaft 16 preferably above the center ofthe operating shaft 14.- The shaft 16 mounts a U-shaped bracket 17thereon which bracket is adapted to carry upon the exterior side thereofmercury tube switches 18 ate the switches by means of a resilient member20 centrally bent back upon itself and then flared outwardly at itsextremities somewhat in the shape of a wish-bone. The outwardly flaredextremities are provided with apertures through which the shaft 16passes and the member 20 is adapted to bear firmly against the interiorportions of the member 1'7 about the shaft 16, and if desired, may beassisted in maintaining contact therewith by interposing a coil spring21 about the shaft between the inner sides of the extremities of themember 20, so that upon an upward or downward movement being impartedto'the outer end of the member 20, the U-shaped'bracket will be causedto travel therewith. The movement imparted to the operating shaft 14 bythe expansion and contraction of the member 11 is transmitted to themember 20 through an operating lever 22 having a pivotal connection 22*intermediate its ends with the shaft 14, pivoted at one extremity by pin22" to the bracket 15 and at the other extremity by pin 22 to anoperating link 23, which is pivoted at its other end 23 to the member20, as shown in Figure 6, whereby an expansion of the member 11 causesthe outer extremity of the member 20 to rotate in an upward directionabout the shaft 16 and a downward movement caused by contraction of themember 11 will impart a reverse movement to the member 20. A stop isprovided to limit the amount of rotation of the U-shaped member 17 aboutthe shaft 16, a preferable form of which is illustrated in Figures 4 and5, ascomprising an upward extension 24 of the bracket 15, the upper end24 of which is bent over in the direction of the center of the plate 9and two adjustable stop screws 25 and 26 are mounted in the bent overportion on each side of the vertical plate passing through the center ofthe shaft 16. This side 1'7 ofv the U-shaped member 17 is extendedbeyond the shaft 16 and the lower ends of the stop screws 25 and 26 areso adjusted that one stop be engaged by the upper edge of the member1'7, when it is rotated in one direction about the shaft 16, and theother stop be engaged by the member 17, when it is rotated in thereverse direction, whereby the amount of rotation is adjusted to thatnecessary to operate the mercury tube switches carried upon said member.

Expansible and contractible members, such as employed herein, aredelicate instrumentalities and to prolong their life and positiveoperation,

it is desirable to allow them to expand and contract freely. For thisreason the switch operating member 17 is provided with the resilientmember 20 interposed between it and the expansible and contractiblemember so that when the rotation of member 17 is limited by engagingeither of the stops 25 and 26, further movement of the member 20 ispermitted'by its frictional contact with the member 1'7, this frictionalcontact being sufficient so that upon" a movement of the member 20 inthe opposite direction will be immediately imparted to the switchcarrying member 17 whereby the switches supported on zaid member will betilted in the opposite direcion.

Referring to the wiring diagram illu trated upon Figure 3, it is seenthat the primary of the transformer 6 is connected in parallel with thecommercial circuit indicated by the wires L and L The secondary circuitfrom the transformer 6 passes through a room thermostat T of commercialform. In order to allow the temperature of the room to control theoperation of the liquid fuel burner, a strip of thermostatic metal 27 isfixedly mounted at one end upon the casing 4 with its free end adaptedto operatively engage the stem 5 of the fuel supply valve. An electricalheating element 28, preferably comprising a plurality of coils ofresistance wires wrapped about said thermostatic member 27, is providedin the secondary circuit adapted to be closed by the room thermostatwhen it is desired tooperate the burner. The energization of the heatingelement 28 will cause the bi-metal strip 2'7 to deform and open the fuelsupply valve through the stem 5 and upon the de-energization of theheating element 28, as the strip 27 cools and returns to normal, willclose the fuel supply valve. The

electric heating element 28 is connected in circuit with the roomthermostat and also with the heating element 10 of the switch operatingmechanism. As illustrated in the diagram, the

mercury tube switch 19 controls the circuit be-- tweenthe commercialline and the electric motor 1. .The switch controlling mechanism,illustrated in Figures 4, 5, and 6, is so arranged that the mercury tubeswitch 19 will be held in the open position whenthe motor is idle.

When the switch 18 is omitted and when the room thermostat calls forheat and closes the secondary circuit, the current will pass from thetransformer 6 through the thermostat T, heat coil 28 to the heat coil 10and thence back to the transformer, whereby heat coil 28 is energizedand causes the oil'valve, by means of thermostatic strip 27, to open andthe heat coil 10 is also energized and causes the motor to operate, bythe expansion of the element 11 imparting an upward movement to themember 20 through operating shaft 14, operating lever 22 and link 23,tilting the mercury tube switch 19 to closed position. It is seen thatthis circuit alone will control the operation of the oil burner and thatas long as the burner remains in operation, the heat coils 28 and 10will be energized and therefore the expansible and contractible member11 will be maintained in its expanded condition. If the movement of themember 11 in expanding, due to the influence of the heat coil 10, isnormally greater than that necessary to tilt the mercury tube switch andno provision is made to allow the member 11 to expand freely, it willthen be exerting a pressure against the stop screw, which pressure willcontinue as long as the burner is in operation and, inasmuch as domesticburners for heating purposes in dwellings are caused to operateintermittently, the expansible and contractible element 11 will beintermittently subjected to such a retarding influence to its normalexpansion. By the arrangement above described, the sliding or frictionalconnection between the switch operating bracket 17 and the pressureactuated member 20 will first tilt the switch until its movement islimited by the stop screw and then the frictional connection will allowfurther expansion of the member 11 without impairing its life oreffectiveness.

When the desired temperature has been reached in the room which causesthe thermostat to break the secondary circuit, the heating coils 28 and10 will be de-energized and the thermostatic strip 2'7 in cooling willclose the oil valve and the expansible and contractible element 11 incooling will tilt the mercury tube switch 19 to open position andthereby stop the motor.

Under certain conditions, it is desirable to delay the operation of theoil valve until after the motor is in operation, and, such a delay ismade possible by providing a mercury tube switch in circuit between theroom thermostat and heat coil 10, which, when closed, will shunt out theheat coil 28. Such a switch is shown in the wiring diagram as indicatedby the reference numeral 18 which is normally closed when the motorswitch 19 is normally open. The switch 18 is mounted upon the oppositeside of the switch carrying bracket 17 in this manner, as shown inFigures 4, 5, and 6. The shunt switch 18 being normally supported uponthe switch mechanism in the closed position while the motor switch is inthe open position, it is seen that,

when the room thermostat calls for heat and closesthe secondary circuit,the secondary circuit is closed through the shunt containing the switch18 and thereby causes the immediate energize.- tion of the heat coil 10,which, in turn, operates the switch mechanism to close the motor switchand open the shunt switch. The motor begins to operate immediately andforces additionalair through the casing 2, however, the oil valve doesnot open until the heat coil 28, now placed in circuit with the coil whythe opening of the shunt switch 18, deforms the thermostatic strip 27 toopen it, and thereby the operation of the oil valve is delayed untilafter the motor is inoperation.

What I claim is:

In a control for an electrically operated liquid fuel burning deviceincluding a motor and a fuel line to the source of supply, thecombination with .a normally open motor switch and a nor- .mally closedfuel valve in the fuel line, of temperature actuated mechanism adaptedto operate the said switch and valve having electrical heating elementsadjacent thereto, a control switch in circuit with said heatingelements, and a normally closedswitch in a shunt-circuit about theheating element for operating the fuel valve mechanism carried upon themechanism for operating the motor switch, whereby, upon closing thecontrol switch the heating element for the valve is shunted out and theheating element for the switch mechanism is energized causing the motorswitch "to be closed and the shunt switch to be opened, thereby startingthe motor and energizing the heating element to operate the mechanism toopen the fuel valve after'the motor. is in operation, and upon openingthe control switch to return the switches and valve to normal position.v

WALTER W. WILLIAMS.

